From the 1860s onwards, it was noted that some patients who had suffered a brain injury or a cerebral vascular injury lost the ability to read and speak, a condition known as aphasia. Kussmal, a German physician noted that the ability to read might be lost independent of the ability to see or speak. He called this condition alexia or "word-blindness". As more and more cases were reported, two different types of word-blindness were found. In one type, a person could not read nor write, and in the other, the person was able to write but was still unable to read. When the brains of these patients were studied, they revealed lesions or hemorrhages in the occipito-parietal region.

In 1891, a case, reported by Dr. Dejerne, described a patient who had become aphasic, alexic, and agraphic after a cerebral vascular accident. After several years had passed, the patient regained the ability to read and speak, but was still unable to write and had poor comprehension skills. A post- mortem examination of several similar patients revealed a brain lesion in every case. This lesion, located in the posterior temporal region, affected the left hemisphere where the parietal and occipital lobes come together. Another early case of dyslexia, reported in The Lancet in 1895, described a fourteen year-old boy, Percy, who was diagnosed with congenital word blindness. Although Percy was described as bright, healthy and skilled at arithmetic, he had difficulty reading and writing. In 1897, several cases similar to that of Percy were investigated and prompted several publishings of case studies. One case suggested that cerebral damage may cause word-blindness, and that birth injury was a predisposing factor (Fisher 1905, 1910).

Later studies by Hinshelwood described word-blindness as a congenital defect. He stated that the disorder was one that occurred in children with otherwise normal brains. Hinshelwood suggested that this disorder was not an organic defect, but that it resulted from abnormal brain development, particularly of the angular gyrus. This brain abnormality affected visual memory of words, letters, and figures. Hinshelwood argued that in place of the natural processing of letters, dyslexics use an auditory system to translate letters to visual memory. Dyslexic learners initially use a sound or analytical coding system, and eventually attach meaning to written words. Hinshelwood, therefore, argued that most teaching methods are inappropriate for dyslexics. He suggested that, instead, a phonetic approach should be used, which allows the reader to use auditory memory to form words.

Another important contribution to the understanding of dyslexia was made by an American psychiatrist and neurologist, Samuel Orton. He observed reading and writing disorders in ambidextrous children and found that most had a tendency to reverse letters and transpose their order. He named this condition named Strephosymbolia. Orton also coined the terms, developmental word deafness (difficulty recognizing spoken word, delayed and confused speech), developmental motor aphasia (slow development and disorders of speech) and developmental alexia (an unusual difficulty in learning to read with no accompanying physical or mental abnormalities), which served as precursors for contemporary categories. (Piorzzado, Wittrock)